Optical instrument for use in aircraft for visually synchronizing the landing wheelsand ground movement



Sept. 13, 1949. s. s. KNOX 2,481,600

OPTICAL INSTRUMENT FOR USE IN AIRCRAFT FOR VISUALLY SYNCHRONIZING THE LANDING WHEELS AND GROUND MOVEMENT 2 Sheets-Sheet 1 Filed July 6, 1945 INVENTOR.

Sept. 13, 1949. s. s. KNOX 2,481,600

OPTICAL INSTRUMENT FOR USE IN AIRCRAFT FOR VISUALLY SYNCHRONIZING THE LANDING WHEELS AND GROUND MOVEMENT 2 Sheets-Sheet 2 Filed July 6, 1945 ,mmm,

Patented Sept. 13, 1949 -OPTICAL INSTRUMENT FOR USE 'IN AIR- CRAFT FOR VISUALLY SYNCHRONIZING THE LANDING WHEELS AND GROUND -MOVEMENT Samuel S. Knox, Long Beach, C.alif.

Application July 6, 1945, Serial No. '6Q3A5D 6 Claims.

This invention has \todo with an aircraft instrument and is -more specifically concerned with an instrument or unit-of apparatus for indicating the operative relationship between the ground and the landing W118B1S'0f .an aeroplane, and it is a general object of the present invention to provide a simple, practical, effective instrument of this general-character.

Certain structures in this application are shown in my prior Patent No. 2,413,924, dated January '7, 1947.

This instrument is intended for use only on large aeroplanes that carry a pilot, copilot and flight engineer as part of their crew.

In landing aeroplanes, and particularly when handling large vaeroplanes, difiiculties are frequently encountered when there is a substantial difference between :the rotational speed of the treads of'the landingwheelsand the movement of the plane over the ground, commonly termed the ground speed.

To facilitate landing various means havebeen proposed and used to eifect'pre-rotation of the landing wheels of planes so that the rotational speeds of theperipheries of the wheels are substantially equal to-the ground speed or to the speed of movement of theplane relative to the ground. Even with such mire-rotation of the landing wheels difficulties are experienced due to differences in speedbetween the several landing wheels, and due tothe fact that it is-practically impossible to gain exactly the same speed between the wheelsandthe ground. Reliance ofa pilot upon pre-rotation is very likely to cause dimculty, whereas-if thepilot is fully apprized of th lack of synchronism in-the various factors involvedhe is-preparedto handle the aeroplane accordingly.

It is a general object-of my presentinvention to provide an instrument whereby thewheel and ground speed may-be observed and compared, and Where power drive is employed to rotate the wheels, be synchronizedawith each other, thus making easier asafeand proper landing. With the knowledge gained from the instrument I have provided theshock of landing can be minimized, making-landings safeand making it possible to'lighten planeconstruction.

Itis another objectiofrmy inventionto provide apparatus such as I havereferred to which'is an optical instrument,orin whichthe factors are communicated {to the sobserver visually, 'making it unnecessaryforrhim to -read or compare instruments or: indicators, such zasspeedometers or other like devices.

.2 Another object of :the invention is .to provide an instrument of v.the general character hereinabove referred ;to which is wholly .free of mechanicallymovingoroperating ,parts complicated or expensiveof manufacture or subject .to failure. The instrument that I have provided .in volves elements that areextremely simple-and inexpensive of .manufacture and when ,once installed vare not subject to improper operation.

Anotherobject ofmyinvention is toprovide a visual or optical instrument of the general character hereinaboye referred .to, .operable at .night as well as duringlthenday. .My invention provides illuminating ;means .making .the instrument, useful even though the parts to be viewed arenot illuminated by daylight.

Another object oimy invention is to provide'a means by which tl'ie synchronizing controls may be operated entirely automatically. This ,automaticcontrol :will .operate 1 at night vas well as during the'day.

The various Obj cots1 and Jeatures of ,my invention will be-fullyzunderstoodcfmm thefollowing detailed description of a typical preferred form and "application of ;the @invention, throughout which description .reference is made ;to the accompanying drawings, in .which:

Fig. l is a plan view of a -;typical ;unit of apparatus embodying the present invention, showing the mannergin which suchunit 'isrelated to a typical aeroplane. Fig.2 ds-a-gfront end -.view of thevisualrapparatus of the present invention likewise indicating its application to atypical aeroplane. jFig.,-3 -8511 enlarged detailed sectional view of one portion; of the apparatus that I have provided. :a :detailed secti a view showing aWQT-tmflhQrQS sectio of" part i I 3 taken on the transversercenter dine. Fig. 5 1 is a plan view .or file. .4. :Fi -6 is .a sectiona vi w taken on the :yertioal ;center ,line of the lower part of Fig.4

Fig. '7 is a "front:end-, view. of tlne automatic synchronizing. apparatusashown symbolically, of the present. invention vlikewise;indicating its application to a typical aeroplane.

Fig. .8 is ;.a: sectional view of the viewingtube used for automatic .pontrol.

Fig.- 9 shows fi mb'olicallyone of the many electrical circuits that may be used towsynchronize wheel and ground speed automatic-ally.

For automatic control cit will be necessary ;to adopt aastan'dardfs zedftire.ethenpnfthe landing strip and the, approach to rthel landing strip for a suitabledistance, reierence-lines; are drawn; so

with its wheels C lowered to theirlanding 13051-1.

tion, the telescopic viewing tube 2 l shown in Fig. 8, cuts across a given number of reference lines per second. As each mark is passed over'a flash of light will occur on the sensitized plateo'f the photo-electric cell 22. This willcausea current to flow in the photo-electric cell circuit 32. This current will be amplified by the amplifier 33, and

synchronized and passing through a suitably geared electric motor 38 will cause each'wheel C to make one complete revolution. Therefore, we get one revolutionof the wheels each time a reference line is passed over and when the wheels touch the runway they will be turning at exactly ground speed.

I show two synchronizing devices in this circuit, one 34 to synchronize the power circuit 35 with the photo-electric circuit 32 and the other 35 to synchronize the wheels 0 with each other. This is desirable as one wheel may turn less freely than the other due to a dragging brake or other mechanical trouble. The lamps 31 will be dark when the wheels are synchronized with each other. 7

Referring in detail to Fig. 8, the lenses 2d and form a Galilean type of telescope. This type of telescope gives a'good enlargement of a small field of'vision. This is desirable as it is necessary to see but one reference line at a time just 'prior to landing. Thecondensing lens 23 is placed over landing strips that have been cross lined.

for automatic control, when it isipreferable to use the manual control.- r r The instrument that I- have provided is useful, generally, on aircraft to facilitate the landing thereof. The invention is particularly useful on{ 65 In the drawings I" have shown two simple typical forms of the in aeroplanes or heavierthan air craft which have to be landed at high speeds.

vention and have indicated such forms of the invention as applied to a typical aeroplane. The aeroplane indicated in the'drawings includes a fuselage A with a pilots compartment at B, landvisible in side by side relationship for immediate comparison.

In large aeroplanes that carry a pilot, a copilot and a flight engineer, the viewing device can be placed so that it will be operated by the flight engineer at times when not on automatic control. a 1 1 In practice the essential elements of the invention will vary with the number and location of the objects to be viewed and with the structure of the aeroplane in which the'instrument is in corporated. In an ordinary situation such as I have illustrated in the drawings the observer utilizing the information is supplied with the de sired information when supplied with a view of. each of the two wheels C and the ground over whichthe aeroplane is traveling. In this particular case the viewing device is such as to provide three images to be viewed by the observer and there are three separate parts to the means ll,

one for projecting an image of the ground over which the plane is operating and one for pro jecting an image of each wheel C.

The particular'viewing device shown in the drawings involves, generally, a case l2, tubular; in form and provided at its upper end with a screen or ground'glass l3. The tubular case is provided with partitionsl-tl which extend longitudinally therein and divide the case into three light ducts or passages X, YandZ. The light;

ducts extend from the lower end of the case to" the upper end where they are open to the ground glass l3.

Each of these several separate parts of the means It includes a light conveying tube 20 having one end facing anobject to be viewed andthe other end facing one of the light ducts of the means I0. Thelight conveying tubes 20 will, in practice, vary in "shape and extent depending upon the relationship of the means It to-the parts to be viewed. In, the particular case illus-" trated, which is a typical case, the tube 20 of one part of means ltdesigned to face the ground: over which the plane is" operated, may be a straight tube extending downwardly from one of the light ducts of means I'll, preferably the center light duct Y of the'rneans lll, as shown in Fig. 2 of the drawings. -This light conveying tube; 29 is joined to the case I2 of means Ill and is open at each end and is free of obstructions so that light reflected from the ground over which the ing wheels C located beneath wing'W in opposite directions from or at either side of the fuselage, Q

the wheels C being carried by a suitable supporting gear D so that they are retractable and so that they are spaced a substantial distance apart laterally of the plane when lowered to be in operating position, as shown in-Fig.2 and Fig. '7 of the drawings.

generally, what I will term a viewingdevice l5 located so that it'can bereadily observed, and

cut objects into the viewing device to be there '70 The instrument that I have provided involves,

plane is traveling; enters the open lower end of the tube and passes'upwardly'through the tube to be passed therefrom into the duct Yin case l2;

In the arrangement illustrated'the viewing de- I vice H1 is located between'the wheels C. E'ach' light conveying tube provided for receiving light from a wheel C has an outer end portion'30 which is vertically disposed over the wheel, a horizontal;

outer portion 30' of each tube is preferably lo Y cated to point to or to face the center'of" the wheel at which it is located; The lateralportio'ns;

3| being'connec'ted at their innerends to the case- E2 of means 10, the said portionof'one'such light conveying tube communicating with duct X-while the said portion of the other light eonveying tube communicates with duct '2. i I provide reflectors at the corners where the light conveying tube portions join so that light entering the lower ends of'the tube portions 30 is reflected through the several portions of the tubes to enter the ducts X and Z; 1 1 I 4 The-means -l-I ihc liides in autiition to tne'tube's hereinabo've described a conden'sing lehs ll in connection with ea-ch tube, preferably where it joins a ductofthe case I B;the-several lenses being such as to receive images from the tubes andthrow or projec't them throu'gh the-duets of case I2 onto the ground glass I3-.

The back or lowerface of parts A I in theouter light ducts X and Z-a-r'e ground at a slig'ht angle such that-the reirac-tion of the glass "Will bend thelight rays assing throughthe-lens enough to give the-proper direbtiontb theprojected image on the ground glass I3. v

It is-to beunde'rstoodthat the tubes or various light conveying parts may, inpractiee. be of any desired shape or cross sectional configuration. In the preferrediorm of-the invention the several t'ubesof the means '1] may be in a'de fairly large in cross sectional extent to pass a substantial amount of-light,='and it may not be desirable to cast images on the ground glass as large as the cross sectional areas of the tubes. In such case'the case I2 maybe-made tapered-croonvergent so that the end where the ground glass is located is substantially smaller than the end to which the several tubes of means I I are joined, and the lenses 4| providedin'the means I i be designed to cast images of the :desired size the ground glass I'3. Y

In practice it is necessary thatithe movements indicated on thegroundglass' I3,' that isthe images of the Wheels and of theiground, should appear to be in the same directionso' that the pilot can readily compare them. =1o accomplish this when the arrangement is such as I have shown in the drawings I provide a reversing prism in the tube passing the image ofthe'ground so that this image is reversed as otherwise it would be moving in a direction opposite to that of the wheels.

In accordance with the preferred form of my invention I provide a source of: light, preferably a small spotlight, 6!! at or near the outer end of each of the tubes and lower end of tube 20 of means I I and the lights are focused and directed so that when they are energized they shine brightly upon the spot from which light is desired to be reflected into the tubes. For instance the light on the center tube which faces the ground shines downwardly onto the ground immediately under that tube, whereas the other lights shine onto the wheels C immediately under or in line with the light conveying tubes facing the wheels.

In the drawings I have indicated a pre-rotating unit G at each landing wheel and have shown a control 98 in the aeroplane adjacent the viewin unit II]. I have indicated the control 9!! coupled with each unit G by a suitable control connection 9| and have shown individual control levers 92 at the control 90 so that the wheels can be individually controlled.

It will be apparent from the foregoing description that the apparatus may be made wholly automatic, that is, through electronic means or other suitable means such as the electric svnchrm nizing circuit shown in Fig. 9, flashing effect of the viewing device can be utilized as the means or medium for effecting adjustment of the prerotation units. For instance, an electronic unit or units can be provided to operate under control of the flashes to regulate the pre-rotation units so that the pre-rotating means are automatically adjusted so that the wheels of the aeroplane are operating in true synchronism B with the ground speed :when the aerdpiane reaches the groun'd. V

With the apparatus thatl have provi'tied light from the several objects, thatis, the we wheels C and from the surface of the; landing field immediately under the plane; is reflected through the tubes of the means I I a'n'd is directedbetween lenses 4I so that severalima'ges arethrow-n-bn the ground glass I3. These-several images clran acterized by the flashes or flash-like eflectmineu by the provision of the reference'marks on the field and wheels, givetheobservera view of the objects to which the'tubes of the means itl are faced.

From the foregoing 'description it'will b'e ap parent that I have provided an'opti'cal itlstrm ment which is entirely fre'ecrworkingor movmg parts subject to failure or whi'ch 'are heavy 'ran'd complicated. The apparatus that rrz haverprm vided, when once properly installed-,rehrains static and is at all times available foi -use. ther, it is important that the instrument-thaw: have provided is whollyoptioal and is -Suh that it can be read instantaneously anddoes notnave to be compared with numerousniais orinstrin ment readings in orderto ascertainme information desired.

Having described only.a-typical-preferredform and application of my invention, l do' not 'wis'h to be limited or restricted-to tners'pe'ci-fi'craetaus herein set forthfbut wish'to reservetc myself any variations or modifications tnatmay appear to those skilled in the art or'fallwithin the sco'pe of the following claims.

Having described my inventiongi claim'z 1. In an airplane including landing wheels, having controlled power means to cl-rii e said wheels at the desired speed "o'f rot'ation, :ineans to synchronize the movementof th'e wheels -and the ground motion relative to tne-airp1ane,-.a viewing device having a ground glass, ositioned at a control point of the airplane, means to project images of the landing'wheels and the ground on the ground glass for simultaneous viewing and comparison, said last named means including a tube to pass light for each image and a projecting lens throwing an image from the tube to the viewing device.

2. In an airplane including landing wheels, having controlled power means to drive said wheels at the desired speed of rotation, a viewing device having a ground glass, positioned at a control point of the airplane means for projecting images of the periphery of the rotating landing wheels and of the ground on the ground glass for simultaneous viewing and comparison, said projecting means including means for causing said movement of the images of the periphery of the wheels and of the ground to be in the same direction, whereby the apparent movement of the periphery of the wheels and of the ground may be synchronized to thereby aid in the landing of the airplane.

3. In an airplane including landing wheels, having controlled power means to drive said wheels at the desired speed of rotation, a viewing device having a ground glass, positioned at a control point of the airplane means for projecting images of the periphery of the rotating landing wheels and of the ground on the ground glass for simultaneous viewing and comparison, said projecting means including means for causing said movement of the images of the periphery of the wheels and of the ground to be in the same direction, whereby the apparent movement of the having controlled 'power means, to drive said wheels at the, desired speed of rotation, a viewing device having a ground glass, positioned at a control point of the airplane means for project ing images of the periphery of the rotating landing wheels and of the ground on the ground glass for simultaneous viewing and comparison, said projecting means including means for causing said movement of the images of the periphery of the wheels and of the ground to be in the same direction, whereby the apparent movement of the periphery of thewheels and of the ground maybe synchronized to thereby aid in the landing of the airplane, and means to illuminate the landing wheels and the ground, said illuminating means including a light adjacent to the lower'ends of the viewing devicer V 5. In an airplane including landing wheels, having controlled power means to drive said wheels at the desired speed of rotation, the speed of. the wheels being synchronous-with the apparent ground motion, a reference mark on the periphery of each landing wheel, an optical viewing device having a ground glass positioned at a control'point of the airplane and observable from within the airplane means for projecting images of the periphery of the rotating landing wheels and of the ground on the ground glass for simultaneous viewing and comparison, said projecting means including means for causing said movement of the images of the periphery of the wheels and of the ground to be in the same direction; whereby the apparent movement :of' the periphery of the wheels and of the groundmay be synchronized to thereby aid in the landingof the airplane. i

6. In an airplane including landing wheels; having controlled power means to drive'said wheels at the desired speed of rotation, the speed of the wheels being synchronous with the an parent ground motion, a reference markon the periphery of each landing wheel, an optical view- 'ing device having a ground glass positioned at a control point of the airplane and observable from within the airplane means for projecting images of the periphery of the rotating landing wheels and of the ground on the ground glass for simul taneous viewing and comparison, the viewing device including a tube for passing light for each image, a reversing prism and a projecting lens directing an image on to the ground glass, Whereby the images of theperiphery of the wheels and of the ground appear to move in the same direction, whereby the apparent movement of the'pe-, riphery of the wheels and of the ground may be synchronized to thereby aid in the landing of the airplane.

SAMUEL S. KNOX.

, REFERENCES CITED I The following references are of record in the file of thispatent: I

UNI'IED STATESPATENTS Number v Name Date 1,142,274 Routin'; June 8, 1915 1,509,167 Morse Sept. 23,1924 1,573,333 Stoll er Feb. 16, 1926 1,745,933 Kauch et a1. Feb. 4, 1930 1,963,826 Chilton June 19, 1934 2,019,234 Nistri Oct. 29, 1935 2,153,718 Kitroser Apr. 11, 1939 2,347,986 Bowerman May 2, 1944 2,353,380 Adler July 11, 1944 2,399,676 Hols'chuh et al. May 7, 1946 2,413,924 Kno Jan. 7, 1947 FOREIGN PATENTS Number Country Date 640,839 France Apr. 7, 1928 

